Welcome to HCM.
Dark labia in Asians is normal and nothing to worry about. It is genetically and environmentally determined. It is the amount of pigmentation in the skin which decides the colour of the skin. If you do not have itching or excess discharge, it is alright. Fungal infection
in that region can make your skin dark. If you think you have fungal infection, it is better to consult a dermatologist
and get treated appropriately.